Adding Insulation to Your Attic

GENE: Yeah. I’ve got a house, two years old, and it’s got r30 in the attic and when I get up there I kind of look around and I can kind of see little here and there, like the drywall from, you know, between the batts of insulation.

 

TOM: OK.

 

GENE: Is it worthwhile going with another r20? I see some of the websites say this area in the mid-Atlantic should have at least r50 in the attic.

 

TOM: Well, certainly, you can’t have too much insulation; so adding another layer of unfaced fiberglass batts installed perpendicular to the existing insulation is a good idea. The one thing I would caution you to do, though, is to make sure that you have enough ventilation in that space because, if you have insulation without ventilation, it’s going to get damp and humid and that could be a problem for you. So I would make sure that I had at least a continuous ridge and soffit vent so it’s flushing plenty of cold, dry air through that space so I don’t get moisture. Because if you add just two percent moisture to insulation, the r value goes down by about a third.

 

GENE: Yeah, I’ve got a full-length ridge vent and there are a couple of exhaust fans up there, too. Is there an …

 

TOM: Well, the exhaust fans are not the most efficient way to vent an attic. If you’ve got a full-length ridge vent, that’s good. I would also make sure that I have full-length soffit vents or perforated soffits on either side of the overhangs.

 

GENE: I think there’s a pretty good cross-flow up there.

 

TOM: Alright, good.

 

GENE: Is there an advantage to having it blown in as opposed to putting batts?

 

TOM: Not necessarily; both are effective.

 

GENE: I had a contractor give me a price on being blown-in and it seemed to be quite a bit more than if – obvious if I did it myself.

 

TOM: Well, there’s a lot of labor and equipment involved in that. The only thing bad about blown-in is it makes it really hard to do things after the fact if you have to, you know, run a wire or fix something; it’s kind of hard to get around.

 

GENE: And some of them were talking of cellulose and some were talking of rock wool. Does it really make a difference?

 

TOM: I wouldn’t use rock wool; that’s an old technology.

 

GENE: Uh-huh.

 

TOM: Cellulose or fiberglass are really the two materials that are used right now.

 

GENE: Oh, OK. Well, good. Well, I guess I get my money back then by putting another r20 or 30 up there then.

 

TOM: I think it’s a good idea, Gene, and it’s an easy do-it-yourself project, so why not?

 

GENE: Itchy, though.

 

TOM: Itchy. Well, you know, you dress for it, right? (Leslie chuckles)

 

GENE: Yeah, right. (chuckles)

 

LESLIE: And wear some sort of ventilation mask …

 

TOM: Yeah.

 

LESLIE: … and safety goggles.

 

GENE: Oh. Definitely. And a lot of old clothes you can get rid of afterwards.

 

LESLIE: (overlapping voices) Yes.

 

TOM: (overlapping voices) And you know what? I’ll tell you something, Gene. There’s types of insulation now called encapsulated insulation where it’s sort of inside of a ventilated, sort of plastic cover. That’s fine too; that is an unfaced insulation …

 

GENE: OK.

 

TOM: … although – even though it has a wrap around it. It’s a lot more comfortable to handle.

 

GENE: Oh, great.

 

LESLIE: Hey, thanks so much for stopping by The Money Pit.